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Separate out dhcp packet validation into validate_dhcp_packet().

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This commit is contained in:
Nicholas J. Kain 2011-07-01 05:33:12 -04:00
parent 09b5c08b5b
commit 9974cc2f51
1 changed files with 26 additions and 19 deletions
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45
ndhc/packet.c
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@ -492,12 +492,35 @@ void set_listen_none(struct client_state_t *cs)
change_listen_mode(cs, LM_NONE); change_listen_mode(cs, LM_NONE);
} }
static int validate_dhcp_packet(struct client_state_t *cs, int len,
struct dhcpmsg *packet, uint8_t **msg)
{
ssize_t optlen;
if (len < sizeof *packet - sizeof packet->options) {
log_line("Packet is too short to contain magic cookie. Ignoring.");
return 0;
}
if (ntohl(packet->cookie) != DHCP_MAGIC) {
log_line("Packet with bad magic number. Ignoring.");
return 0;
}
if (packet->xid != cs->xid) {
log_line("Packet XID %lx does not equal our XID %lx. Ignoring.",
packet->xid, cs->xid);
return 0;
}
if (!(*msg = get_option_data(packet, DHCP_MESSAGE_TYPE, &optlen))) {
log_line("Packet does not specify a DHCP message type. Ignoring.");
return 0;
}
return 1;
}
void handle_packet(struct client_state_t *cs) void handle_packet(struct client_state_t *cs)
{ {
uint8_t *message = NULL; uint8_t *message = NULL;
int len; int len;
struct dhcpmsg packet; struct dhcpmsg packet;
ssize_t optlen;
if (cs->listenMode == LM_NONE) if (cs->listenMode == LM_NONE)
return; return;
@ -508,29 +531,13 @@ void handle_packet(struct client_state_t *cs)
// Transient issue handled by packet collection functions. // Transient issue handled by packet collection functions.
if (len == -2 || (len == -1 && errno == EINTR)) if (len == -2 || (len == -1 && errno == EINTR))
return; return;
log_error("Error when reading from listening socket: %s. Reopening listening socket.", log_error("Error reading from listening socket: %s. Reopening.",
strerror(errno)); strerror(errno));
change_listen_mode(cs, cs->listenMode); change_listen_mode(cs, cs->listenMode);
} }
if (len < sizeof packet - sizeof packet.options) { if (!validate_dhcp_packet(cs, len, &packet, &message))
log_line("Packet is too short to contain magic cookie. Ignoring.");
return; return;
}
if (ntohl(packet.cookie) != DHCP_MAGIC) {
log_line("Packet with bad magic number. Ignoring.");
return;
}
if (packet.xid != cs->xid) {
log_line("Packet XID %lx does not equal our XID %lx. Ignoring.",
packet.xid, cs->xid);
return;
}
if (!(message = get_option_data(&packet, DHCP_MESSAGE_TYPE, &optlen))) {
log_line("Packet does not specify a DHCP message type. Ignoring.");
return;
}
packet_action(cs, &packet, message); packet_action(cs, &packet, message);
} }